The subject matter disclosed herein relates to refrigeration systems. More specifically, the subject matter disclosed herein relates to compressor oil recovery for refrigeration systems.
Refrigeration systems typically include a compressor delivering compressed refrigerant to a condenser. From the condenser, the refrigerant travels to an expansion valve, and then to an evaporator. From the evaporator, the refrigerant returns to the compressor to be compressed.
The compressor is typically provided with lubricant, such as oil, which is used to lubricate bearing and other running surfaces of the compressor. During operation of the compressor, the lubricant mixes with the refrigerant operated on by the compressor, such that an oil/refrigerant mixture leaves the compressor and flows through the refrigerant system. This is undesirable, as the mixing of oil with the refrigerant flowing through the system makes it difficult to maintain an adequate supply of oil at the compressor for lubrication of the compressor surfaces. In some systems, oil separators are used immediately downstream of the compressor, but such separators often remove the oil from the mixture at a high pressure, and in many instances still include an appreciable amount of refrigerant mixed with the oil, resulting in a lower viscosity of oil at the compressor.
Other systems use electric heaters to vaporize the refrigerant from the oil/refrigerant mixture, but consequently return a heated oil to the compressor, having a reduced viscosity due at least in part to its higher temperature.